explain the difference between a homophonic pun and a homographic pun

A homophonic pun is a play on words that uses words that sound the same but have different meanings. For example, "I'm reading a book about anti-gravity. It's impossible to put down!" is a homophonic pun because the phrase "put down" can mean both to pick up a book and to stop reading it.

A homographic pun is a play on words that uses words that are spelled the same but have different meanings. For example, "I'm going to the bank to deposit my paycheck" is a homographic pun because the word "deposit" can mean both to put money into a bank account and to leave something somewhere.